This invention is directed to marker lights, and more particularly to light emitting diode type marker lights that are flexible and liquid tight and are resistant to damage caused impacts, abrasion or exposure to extreme environmental elements.
This invention generally relates to impact and shock resistant marker lights comprising encapsulated light sources. Marker lights used in applications such as off road vehicles are subjected to extreme abuse such as vibration created by traversing rough terrain and direct exposure to the elements such as rain, mud and dust plus an occasional impact with a tree branch or a vehicle crash. In particular, it relates to such lights wherein one or more light emitting diode (LED) light sources and a structural protective member with an integral wiring harness surrounding the LED""s are encapsulated by injection molding a transparent or semi-opaque thermoplastic elastomeric resin casing around them.
Description of the Prior Art
Marker lights currently utilize short life span incandescent bulbs as the primary means for producing light. Incandescent bulbs require high wattage for operation due to their inefficient nature of energy to light conversion as most energy ends up as waste heat. Most incandescent type marker lights have a removable lens to allow bulb replacement and thus are not sealed to be completely water, dust or mud proof Marker lights with incandescent filament type bulbs exhibit a reduction in bulb life when exposed to vibration, water and impacts encountered during off road use. Filament lamps have many drawbacks such as high power consumption, generating large amount of heat and filament breakage, the lamps per se being large and heavy. Existing marker light housings are constructed of semi-rigid plastics which are not inherently flexible, have low izod impact strengths and thus demonstrate a propensity to substain permanent damage during impacts. Incandescent type marker lights are also large and bulky due to the inner housing design which generally utilizes a metal carrier to hold the hot bulb and act as heat sink while also providing a means for bulb retention and replacement. The metal carrier that secures the bulb has a tendency to corrode over time due to water condensation in the bulb housing. The corroded electrical contacts of the metal carrier can produce a degraded intermittent light circuit connection or a possible open circuit. Incandescent marker lights usually have a separate transparent tinted lens assembly surrounding the incandescent bulb that is molded from low impact resistant styrene, polycarbonate or acrylic and thus is fragile and breaks easily when subjected to impacts. Therefore it would be beneficial to have an improved marker light without the problems described.
The purpose of the present invention is to provide a zero maintenance marker light of the aforesaid type that is impact, shock, and abrasion resistant while also increasing the overall marker light operational life, while reducing weight and power requirements. The marker light design must be producible utilizing high volume production methods such as injection molding, wave soldering and presswork operations. This purpose is met by this invention, which is characterized by the fact that the marker light casing is injection molded utilizing a tough elastomeric plastic polymer that is molded around the LED""s, the LED protective structure and LED wiring harness such that the marker light constitutes a non-dismountable whole. This results in a completely liquid tight encapsulation with combined electrical insulation and resistance to extreme mechanical stresses such as impacts, vibration and abrasions. Since the light output of an LED is a reduced by high humidity, the complete embedment of the LED by a thermoplastic elastomer prevents moisture ingress. The LED""s with their attached flexible wiring harness and protective structure are insert injection molded around a flexible thermoplastic elastomer The flexible composite assembly created, allows the thermoplastic elastomer casing to attenuate energy during impacts without affecting the LED""s or their associated electrical connections. The marker light casing is composed of highly abrasion resistant elastomeric polymers that do not mar or scratch easily and readily retain their initial shape after impacts. The LED""s used in the marker light are classified as solid state semiconductor devices that have a mean time between failure of approximately 100,000 hours and are not damaged by vibration or shock loads. For added attractiveness and appeal, the thermoplastic elastomer casing can be molded using any semi-opaque color scheme provided it meets optical requirements of SAE J576. The semi-opaque colored casing diffuses the intense focused LED light, increasing the viewing angle and lowering the on axis LED intensity producing a more homogenous and uniform light distribution. The marker light output can also be further enhanced by molding a lens into the casing to diverge the LED light output to produce a marker light high in luminance and wide in viewing while eliminating glare complaints and reducing the number of light emitting diodes required. The LED""s used in the marker light are very efficient devices as they operate on approximately 20 percent of the power required by incandescent bulbs. Vehicle weight is a major design consideration for on-off highway vehicles. Lower weight vehicles have better maneuverability and operator control plus reduced energy consumption and increased vehicle performance. A vehicle""s alternator power output can be reduced using LED lighting technology thus reducing overall vehicle weight. When LED based marker lights are used as emergency flashers utilizing only battery power, the operation time can be increased from two to four times over incandescent lighting technology. This feature provides a safety improvement as well as reducing the likelihood of a dead battery. LED""s are solid state devices so they turn on and off in tens of nanoseconds compared to about 200 milliseconds for an incandescent bulb. This provides the end user a safer signalling device that turns on approximately one car length quicker at highway speeds. Other details and advantages of the present invention will become apparent as the following description of the presently preferred embodiments of practicing the invention proceeds.